1. Field of the Invention
The present invention relates to a roll screen apparatus.
2. Description of the Related Art
A conventional roll screen apparatus which is disclosed in Japanese Patent Application No. Hei 4-80493 comprises a screen-winding axle equipped with an energizing means to apply a rotating force to the screen-winding axle for winding up a screen hanging therefrom, a pulley having an associated operation cord, and a clutch device responsive to the unwinding of the screen by pulling the operation cord for transmitting rotation of the pulley to the screen-winding axle, and responsive to the pulling-down of the operation cord subsequent to the screen-unwinding operation for permitting the energizing means to apply the rotating force to the screen-winding axle, thereby rotating the screen-winding axle to wind up the screen thereon.
The clutch device comprises: a clutch casing fixed to the middle of the support axle so as to permit rotation thereabout but prevent axial displacement therealong, the clutch casing having the output shaft of the pulley fixed thereto, to permit no relative rotation therebetween; a first clutch drum rotatably supported by to the middle of the support axle within the clutch casing; a coil spring connected at one end to the clutch casing and at the other end to the first clutch drum; a second clutch drum provided to the circumference of the base portion of the first clutch drum; a slide groove made on the inner circumference of the clutch casing; a clutch ball between a first guide groove made on the outer circumference of the first clutch drum and a second groove made on the forward end of the second clutch drum, the ball being movable along with rotation of the clutch casing; a brake drum rotatably supported by the middle of the support axle; a brake carrier rotatably supported on the inner circumference of the brake drum, the forward end of the brake carrier being connectable to the first clutch drum; a stop ring fitted on the middle of the support axle, and supported at one end by the brake carrier and at the other end by the first clutch drum; a brake spring fitted on the inner circumference of the brake drum; a coil spring fitted on the outer circumference of the brake drum; and an operation cap extending from the forward end of the clutch case to the base portion of the brake drum to cover the whole length, the forward end of the operation cap being rotatably supported by the forward end of the clutch casing through the agency of bearings, and one end of the coiled spring being connected to the operation cap, the outer circumference of which operation cap has the screen-winding pipe provided thereon.
When it is desired that the screen is unwound, the pulley is rotated in the screen-unwinding direction, thereby permitting the clutch casing to rotate against the energizing force of the coil spring thus to move the clutch ball. Then, rotation of the clutch casing is transmitted to the first clutch drum via the rotating clutch ball, thereby expanding radially the stop spring until it is allowed to rotate about the support axle along with the first clutch drum, and therefore, the first clutch drum presses against the brake carrier until it rotates, causing the brake spring to expand radially. Thus, the brake drum rotates together, permitting the screen-winding axle to rotate through the operation cap.
When it is desired that the screen is wound up, the pulley is rotated in the screen-unwinding direction, thereby permitting the clutch casing to rotate against the energizing force of the coiled spring thus to move the clutch ball. Then, rotation of the clutch casing is transmitted to the second clutch drum via the rotating clutch ball, thereby allowing the second clutch drum to press against the end of the brake ring until it rotates in the screen-unwinding direction. Rotation of the brake ring is transmitted to the brake carrier via the brake spring, and accordingly the friction between the support axle and the stop spring increases until the brake carrier is fixed to the support axle. While one end of the brake spring is fixed to the brake carrier, the other end of the brake carrier is increasingly pressed to cause radial reduction of the brake spring, accordingly lowering the friction between the brake spring and the brake drum until the brake drum is permitted to rotated with respect to the brake spring. Then, the screen-winding axle is allowed to rotate under the influence of resilience stored in the coil spring, thereby winding up the screen.
Likewise, a roll screen apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 4-149390 includes a screen-winding axle having a screen to be wound and unwound therefrom, an energizing means to apply a rotating force to the screen-winding axle for winding up the screen hanging therefrom, a pulley operatively connected to the screen-winding axle for rotating it, and an associated operation cord for rotating the pulley. When it is desired that the screen is unwound from the screen-winding axle, the unwinding or "down" side of the operation cord is pulled down to tighten an associated clutch spring, thereby connecting the pulley to the screen-winding axle for transmitting rotation of the pulley to the screen-winding axle. When it is desired that the screen is wound on the screen-winding axle, the winding or "up" side of the operation cord is pulled down to rotate the pulley in the direction in which the screen is wound on the screen-winding axle, thereby loosening the clutch spring to disconnect the pulley from the screen-winding axle. Then, the screen-winding axle is allowed to rotate and wind up the screen by the self-contained energizing means.
The roll screen apparatus of Japanese Patent Publication No. Sho 63-46224 requires alternate and repetitive succession of pulling-down and winding-up of the cord. This operation causes inconvenience.
The roll screen apparatus to Japanese Patent Application Laid-Open No. Hei 4-80493 uses a clutch device, which is composed of numerous parts, and is complicated in structure. Accordingly, the assembling work cannot be simplified and the efficiency of labor is not good, requiring high production cost.
These conventional roll screen apparatuses use a clutch spring responsive to application of a rotation force to the pulley for disconnecting the pulley from the screen-winding axle against the resilient force of the energizing means. This necessitates increased resilient force of the energizing means with increase in the screen size, and accordingly the counter resilient force of the clutch spring must be increased. The rotating force to be applied to the pulley, therefore, increases, and disadvantageously the cord load increases for operation. Specifically, a small-sized screen can be wound by a reduced torque, and therefore, the self-contained energizing means and clutch spring need not generate strong resilient force. On the contrary, a large-sized screen requires an increased torque for winding up, and accordingly, an increased resilient force must be produced by the self-contained energizing means and clutch spring. It is, therefore, necessary to select and use clutch springs of different strengths to meet energizing means of different resilient strengths, and apparently, this is inconvenient to a production process, accordingly lowering the productivity. Apparently the mismatching of the clutch spring with the energizing means can be a cause for trouble. The number of the kinds of clutch springs increases with the increase of the kinds of energizing means, and the increased number of parts does not favor the manufacturing cost. In an attempt to reduce the numerous kinds of parts in number, it is proposed that clutch springs whose resilient force meets the strongest resilient force of energizing means appropriate for winding up a largest screen are used in common with all screens of different sizes. This approach, however, has a disadvantage of requiring a same, strong force for operating relatively small-sized roll screen apparatuses.